1. Field of the Invention
The present invention concerns a method to generate visual command data for two-dimensional visualization of a vascular tree of a vascular system from tomography data acquired with an imaging system, as well as a command data derivation system for the same purpose.
2. Description of the Prior Art
The two-dimensional visualization of image data (i.e., tomography data) from vascular systems (especially vascular trees) from an imaging tomography exposure serves to enable a viewer to be shown an overview of the often very complex structures of the respective vascular system. Even when the vascular systems (for example blood vessel systems, but also other vascular systems formed as branching hollow organs, such as the lymphatic system, the bronchial tree or others) exist in a widely branching and correspondingly complex three-dimensional tree structure, the viewer must be able to quickly be given an overview on a screen or using a computer printout. In practice, this overview is inevitably presented in two dimensions. The evaluation of the topology of a vascular tree then forms an important basis of evaluation for the analysis of functional pathologies in medicine. A suitable visualization of the vascular tree hereby represents an essential basis for a qualitative assessment.
However, conventional presentation methods for both two-dimensional and three-dimensional presentation return only a defined section of the total information content of the tomography data. Either losses in clarity arise, or only partial sections of a vascular tree can be presented to the observer at one time. The unfolding of a vascular tree enables the representation of its topology without superposition of structures in a single presentation and is usable in a versatile manner.
Essentially, two methods exist that attempt to present an unfolded vascular tree. In multi-path CPR that is described in Kanitsar A. et al.: “Advanced Curved Planar Reformation Flattening of Vascular Structures” in: IEEE Visualization, IEEE Computer Society Press; 2003. P. 43-50, slices that are projected in one plane are created along a single vascular center line (i.e. a curve line or, respectively, more precisely a center line). The arrangement of adjacent vascular representations subsequently takes place with the aid of recursively circumscribing sub-trees. In the approach from Kiraly et al. (“2D Display of a 3D Tree for Pulmonary Embolism Detection” in: CARS Vol. 1281; 2005. P. 1132-1136), what is known as an intensity projection that is subsequently arranged in a tree diagram is generated along each vascular center line on the basis of the vascular surface. Both methods generate a very schematic representation of the vascular tree. Furthermore, the multi-path CPR is especially more suitable for less complex vascular trees. Exemplary embodiments for this would be pathological cardiac vessels or peripheral vessels. An additional, relevant method generates a slice through a vessel with the aid of Coons surfaces. This approach is described in Saroul L et al.: “Distance Preserving Flattening of Surface Sections” IEEE TVCG, 2006; 12; P. 26-35. These Coons surfaces here are subsequently flattened at a point or, respectively, in a curve of interest. However, this method is only conceived for a single vessel, and not for a vascular tree.